Human cytomegalovirus (that is, ‘HCMV’) belongs to beta-herpesvirus and contains double-stranded DNA with a length of 230 to 240 Kbp, which is the largest of the human viruses. HCMV is a ubiquitous pathogen and found worldwide both in developed industrial societies and in isolated aboriginal groups. Although most of the HCMV infections are not symptomatic, severe clinical outcomes may arise in neonates, immuno-compromised hosts and recipients of organ transplants.
Since HCMV was first and successfully isolated from the salivary glands, adenoid tissues and urine in the 1950's, HCMV isolation has been performed worldwide from various parts of the infected human. Genome-wide analyses of HCMV genetic contents became possible when the genome of the widely used laboratory strain AD169 was fully sequenced by plasmid cloning and a Sanger method. An analysis result of 230 Kbp genome has identified ˜150 to at most up to 192 open reading frames (‘ORFs’), which may potentially encode a protein. Most low-passage strains have 19 ORFs encompassing ˜15 Kbp in UL/b′ region that are absent from the high-passage strain AD169. This region is inverted within the genome relative to its counterpart in AD169.
Due to the large genome size of HCMV, there have been difficulties in obtaining the whole genome sequences of HCMV. As sequencing technologies have recently developed, almost 20 whole genome sequences have been determined for HCMV. Cloning of the entire HCMV genome into bacterial artificial chromosome has enabled analysis of full genome sequences of well-known strains such as Toledo, Towne, TB40/E, etc., as well as clinically isolated ones (‘isolates’) such as FIX, PH and TR. In recent years, high-throughout sequencing technology using Illumina Genome Analyzer has been used to obtain complete genome sequences of Towne and AD169 variants as well as several clinical isolates. In order to determine the whole genome sequences for clinical isolates, polymerase chain reaction (PCR) sequencing techniques have been applied.
Until now, all of the full genome sequences of HCMV isolates are from European countries or the United States, while full genome sequences of HCMV isolated from Asian people, especially, Korean people have not been reported.